1. Field of the Invention
The invention relates to mechanisms for coupling an engine and transaxle to a vehicle frame.
2. Description of the Related Art
Conventional powered vehicles such as lawn and garden tractors provide a power source or engine, and a transaxle that transmits rotational motion from the engine to ground engaging driven wheels. When the transaxle transmits torque to the driven wheels to drive the vehicle forward, an equal and opposite torque load is transmitted to the frame of the vehicle. For example, the transaxles of rear wheel drive vehicles will urge the vehicle frame to rotate upwardly and rearwardly about the rear wheels in response to the vehicle being driven forwardly. A relatively large torque load is thereby transferred to the vehicle frame at the point where the transaxle is coupled to the frame. The vehicle is typically prevented from rotating upwardly and rearwardly by the weight of the vehicle itself. Vehicle frame structures must be strong enough to withstand the large concentrated loads that result from driving torque being applied to the driven wheels. Conventional vehicle frames must also be sufficiently strong to carry the weight of vehicle components such as the engine. Many conventional vehicle frames are manufactured from relatively rigid and strong metal materials such as steel, and therefore easily absorb large concentrated force loads associated with driving torque and engine weight. However, because conventional frame structures must be relatively strong, they are relatively expensive to manufacture and assemble.
A first type of conventional lawn and garden vehicle provides an engine and transaxle that are each separately attached or coupled to the frame. Because the two components are separately carried by the frame, interchangeability of components is possible. Therefore, different sizes of engines, or different types of transaxles can be installed on identical frames during manufacture. However, removal of the engine or transaxle for servicing is relatively difficult since the two parts must be disconnected from each other to allow removal of either component from the vehicle Conventional vehicles often provide a series of belts and pulleys between the engine and transaxle that must be disconnected for removal of either the engine or the transaxle Many engine or transaxle service operations would not otherwise require the two components to be uncoupled from each other, and therefore the process of disconnecting the components from one another is often unnecessary and needlessly time consuming other then to allow removal from the vehicle. This type of conventional vehicle transfers relatively large forces to the frame as a result of driving torque, and may transfer a large portion of the weight of the engine directly to the frame. Therefore strong materials such as steel that can withstand relatively large concentrated loads are typically utilized to manufacture the vehicle frame.
A second type of vehicle provides a unitized engine and transaxle. Vehicles of this type provide engines and transaxles that are integral with each other or unitized, and therefore can be removed from the vehicle without being uncoupled from each other. However, since they are formed integral with each other, interchangeability of components is eliminated. Some of the vehicles of this type position the engines's center of gravity directly over the axle such that the weight of the engine is largely transferred to the axle and wheels rather than to the frame. Therefore the force corresponding to the weight of the engine that is applied to the frame is reduced. However, the concentrated load applied to the frame that results from driving torque being transmitted to the wheels typically remains relatively large, and the frame must therefore be manufactured from a relatively strong material to withstand high concentrated loads.
The two types of vehicles discussed above therefore require the use of a frame that can withstand large concentrated loads due to the torque associated with driving the vehicle. Conventional vehicles may also require the vehicle frame to withstand relatively large concentrated loads associated with the weight of the engine. The vehicles discussed above are therefore particularly unsuitable for use with a light-weight frame structure made of an inexpensive material such as plastic that may not be capable of withstanding high concentrated loads.
It would therefore be desirable to provide a mounting mechanism that transfers relatively small concentrated loads to the frame that result from acceleration of the vehicle. Such a mounting mechanism would allow the vehicle frame structure to be manufactured from relatively inexpensive materials such as plastic. It would also be desirable for such a mechanism to allow the engine to be positioned such that the center of gravity of the engine is vertically aligned with the axle to thereby transfer its weight downwardly to the ground through the axle and ground engaging wheel, rather than through the frame. It would be desirable to provide a mechanism that mounts an engine and transaxle to a frame and that allows interchangeability of components. It would be desirable to provide a mounting mechanism that also increases the ease with which the components can be removed from the vehicle for service, and that allows the engine and transaxle to be removed without requiring the two components be disconnected from one another for removal.